DESCRIPTION: The long-term objective of this research is to optimize benefit from a cochlear implant for individual patients. Availability of new technology provides an opportunity to increase speech recognition for most patients, to develop a theory of parametric manipulation for optimized performance, and to improve poorer performers' speech recognition. In the proposed research, the large multidimensional, parametric space for electrostimulation is divided into the domains of speech processing parameters and fitting parameters. Aim 1 evaluates the effects of changing speech processing parameters (electrode stimulation sites, number of channels, stimulation rate) on speech recognition. Aim 2 evaluates the effects of four fitting parameters (maximum stimulation levels, electrode selection criteria, frequency boundary selection, compression functions) on speech recognition. Aim 3 evaluates the relation between intracochlear electrode position, characteristic frequencies near the electrodes, and speech recognition to address sources of inter-subject variability in speech recognition. Aim 4 monitors longitudinal performance and compares monopolar versus bipolar stimulation. The outcome of this research is intended to improve performance and clinical care of patients with multielectrode, intracochlear implants.